This invention relates to chilling, storing, and shipping of materials which require low temperature maintenance. A primary example of such material is fish.
Food fish require rapid chilling and low temperature maintenance during holding and shipping to maintain their freshness and flesh quality. At the same time, it is highly desirable to reduce handling of fish to a minimum and to prevent excessive pressure on the fish while rapidly chilling a fish and preserving temperatures in precise low ranges.
Historically, fish have been consumed as quickly as possible after harvesting. Cool weather conditions and ice extend the times between catch and consumption, processing and freezing or preserving.
Before the wide availability of ice, it was common for fishing boats to take on quantities of salt which were used to intermix with the fish to preserve the fish until off-loading from a boat. It is common now for fishing vessels to take on a large quantity of ice before enbarking for several days of fishing. As the catch is stored in the hold, ice is intermingled with the fish or fish and ice are stored in alternating layers to preserve the fish at low temperatures until the catch is off-loaded.
Types of fish differ in handling requirement. Some fish may be readily stored at reduced temperatures in the intact form as they are caught. Others require gutting before satisfactory storage. Some fish may be tightly packed to several feet in depth without destroying the qualities of the fish. Values of other fish may be greatly reduced by excessive pressures of overlying fish and ice. Slow cooling of some fish is acceptable, while others require rapid chilling to preserve their valuable qualities. Some fish may not be damaged by handling and conveyor belts associated with bulk storage. Other fish are easily damaged and their value greatly reduced by handling.
As an improvement on bulk storage, several methods of fish handling and storing have been devised. In one such method fish are placed in rough boxes and the boxes are transferred to the hold with a layer of ice being shoveled into the top of each box before the boxes are stacked. Sides of the boxes may partially support the weight, but the great bulk of the weight is supported by the fish within the boxes. Icing may be uneven.
It has been proposed to place a measured quantity of ice in the bottom of boxes and to place the boxes in stacks in ships' holds. The boxes are unstacked, filled with fish, and restacked.
It has also been proposed to place large removable tanks in the holds of ships. Seawater is added to ice in the bottoms of the tanks before fish are chuted through hatches in the tank tops. When the tank is filled, pressurized air is released in the bottom of the tank, bubbling the water melting the ice and stirring the slush through the fish. That system results in rapid chilling of the fish but has an added drawback in that complex handling and emptying equipment is required.
The large bulk of the tanks requires heavy construction which is dead weight as far as cargo is concerned. Smaller containers of the prior art either have little strength or require metal reinforcements and attendant heavy weights to meet strength requirements. Small containers of the prior art have little lateral stability which is especially important in handling and in storing aboard ship. Systems of the prior art include devices which are too large to be handled without special equipment in their empty condition or which are too small to provide economically viable packaging in their loaded condition.
The system of the present invention overcomes and avoids these and other problems of the prior art.
One advantage of this invention is the ability of chilling fresh fish rapidly. While leaving the fish in the container, they may be shipped to any location throughout the world. Without the use of refrigeration, the temperature of the fish will remain very low for a great length of time. The invention itself, as can be seen from the above, is designed at least as much for air transport as well as sea and other modes of transport.